Solar Energy Calculator Sizing Guide
The roof area of your home will be important in determining how many and what sizes of
solar panel you can install. Solar panels are installed in arrays, with the number of panels
varying depending on the roof area available and the amount of power you wish to generate.
Each individual panel usually has an area of 1.3-1.7m2, with 1.6m2 the most common size.
These panels can then be lined up to cover larger areas, and therefore generate more
power.
The smallest array you can have is typically 6 panels (2x3), which would cover 9.6m 2 and
generate around 1.3kW. However, the most common installation is a larger 4kW system,
which would require 18 panels and cover around 28.8m2. Your installer will be able to advise
you on the exact number, type (power rating and size) and arrangement of panels suitable
for your home, ensuring none are placed in shaded areas which don’t receive direct sunlight.
However, the table below shows some typical values for different house types to give you an
idea.
If you don’t have a large available roof space or a south facing roof, it’s also possible to have
ground-based solar panels. These will need to be away from your property to avoid shading,
so are only appropriate if you have a large enough garden.
Typical suitable
roof area (m2)*
Appropriate
number of panels
Period mid-terrace or end terrace
16.5
10 panels (16.0m )
Small semi-detached house
17.0
10 panels (16.0m )
Modern mid terrace or end terrace
18.0
10 panels (16.0m )
Modern 3 storey town house
18.0
10 panels (16.0m )
Average semi-detached house
20.0
12 panels (19.2m )
Small detached house
21.5
12 panels (19.2m )
Old 3 storey town house
23.0
12 panels (19.2m )
Semi-detached bungalow
27.0
16 panels (25.6m )
Two bedroom top floor flat
28.0
16 panels (25.6m )
Average detached house
29.5
18 panels (28.8m )
Detached bungalow
31.0
18 panels (28.8m )
House type
Power rating
(kW)
2
2.2
2
2.2
2
2.2
2
2.2
2
2.6
2
2.6
2
2.6
2
3.5
2
3.5
2
4.0
2
4.0
*This is half the typical roof area in the case of pitched roofs with a 20% allowance for unsuitable installation area
Energy Saving Trust –Version 1 – Feb 2015